Spring systems are used in various applications, for example, to assist in lifting, opening, and damping applications. Typical applications include lifting a lid hinged to a stationary base. Other applications include lifting and/or balancing the hood of a car or trunk or the hatchback of an automobile, shock absorbers for vehicles and machinery, struts for vehicles, etc. Another application of the spring system includes damping the closing of a door hinged to a stationary frame. Many of the struts used are pneumatic or gas springs to assist the opening motion. Many of these types of spring systems contain either gas or hydraulic fluid to control forces and piston speeds. Two types of prior art gas springs are disclosed in U.S. Pat. Nos. 5,887,857 and 6,179,099, both of which are incorporated herein by reference.
Other types of spring systems include one or more mechanical springs. The spring systems can include damper systems that include mechanical springs or either gas or hydraulic fluid. Examples of such spring systems are disclosed in U.S. Pat. No. 6,942,204; United States Patent Publication Nos. 2004/0222579; 2006/0027955; and DE 10244379, all of which are incorporated herein by reference.